A type of rotating disk magnetic field probe

ABSTRACT

A type of rotating disk magnetic field probe (1) comprising: a non-magnetic rotating disk (2), 4N first soft ferromagnetic sectors (3), M second soft ferromagnetic sectors (4), a reference signal generator, an X-axis magnetoresistive sensor (7, 8), a Y-axis magnetoresistive sensor (5,6), and a Z-axis magnetoresistive sensor (9). Both the first soft ferromagnetic sectors (3) and the second soft ferromagnetic sector (4) are located on the non-magnetic rotating disk (2). In operation, the non-magnetic rotating disk (2) rotates about a Z-axis at a frequency f. An external magnetic field is modulated by the first soft ferromagnetic sector (3) into an X-axis magnetic field sensed component and a Y-axis magnetic field sensed component having a frequency of 4N×f, and is modulated by the second soft ferromagnetic field sectors into a Z-axis magnetic field sensed component having a frequency of M×f. The X-axis sensed magnetic field component, the Y-axis sensed magnetic field component, and the Z-axis sensed magnetic field component respectively are converted into output signals by means of the X-axis magnetoresistive sensor (7, 8) the Y-axis magnetoresistive sensor (5, 6) and the Z-axis magnetoresistive sensor (9). The reference signal generator respectively outputs a first reference signal having a frequency of 4N×f and a second reference signal having a frequency of M×f. The first reference signal, the second reference signal, and the measurement signals are demodulated by an external processing circuit to output magnetic field values Hx, Hy and Hz.

TECHNICAL FIELD

This embodiment of the present invention relates to magnetoresistivesensor technologies, and in particular, to a type of rotating diskmagnetic field probe.

BACKGROUND ART

Magnetoresistive sensors have 1/f noise. Reducing the noise ofmagnetoresistive sensors and developing a low noise magnetoresistivesensor are of great significance in improving the accurate measurementof magnetic signals.

In general, magnetoresistive sensors have high 1/f noise at a lowfrequency, while thermal noise is dominates at a high-frequency, but itsnoise energy density is much lower than that of the 1/f noise at the lowfrequency. Therefore, at present, it is common to modulate a magneticsignal into a higher frequency magnetic field, which is then measured bya magnetoresistive sensor to output a high-frequency voltage signal. Thehigh frequency voltage signal is then demodulated, for the purpose ofmoving magnetic signal measurement from a low-frequency part of thespectrum to a high-frequency part of the spectrum, thereby reducing 1/fnoise energy density.

However, existing high-frequency magnetic signal measuring apparatusesgreatly increase the complexity and size of a magnetoresistive sensor,as well as the complexity of the manufacturing process.

The U.S. Pat. No. 365,398 discloses a magnetoresistive sensor method andapparatus for modulating magnetic flux sensed by a magnetic sensor. Thepresent application includes at least one magnetic sensor attached to abase structure, a rotating member, and at least one flux concentratormounted on the rotating member. With the rotation of the rotatingmember, the at least one magnetic flux concentrator periodically shieldsthe magnetic sensor. Thus, the output of the at least one magneticsensor will be modulated. The present application uses a TMR sensor chipto realize a two-axis sensor, which has a complex structure and largesize.

SUMMARY OF THE INVENTION

The embodiments of the present invention provide a type of rotating diskmagnetic field probe to solve the problem of measurement systemcomplexity.

The embodiments of the present invention provide a type of rotating diskmagnetic field probe, including:

a non-magnetic rotating disk, 4N first soft ferromagnetic sectors, and Msecond soft ferromagnetic sectors. Both the first soft ferromagneticsectors and the second soft ferromagnetic sectors are located on thenon-magnetic rotating disk. Cylindrical coordinates of the 4N first softferromagnetic sectors are respectively (r[r₁,r₂], α[Φ₀,90°/N−Φ₀],z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+90°/N,2×90°/N−Φ₀], z[z₀,z₀+th₁]),(r[r₁,r₂], α[Φ₀+(i−1)×90° N,i×90°/N−Φ₀], z[z₀,z₀+th₁]) and (r[r₁,r₂],α[Φ₀+(4N−1)×90°/N,4N×90°/N−Φ₀], z[z₀,z₀+th₁]), and cylindricalcoordinates of the M second soft ferromagnetic sectors are respectively(r[r₃,r₄], α[Φ₁,360°/M−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄],α[Φ₁+360°/M,2×360°/M−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄],α[Φ₁+(i−1)×360°/M,i×360°/M−Φ₁], z[z₁,z₁+th₃]) and (r[r₃,r₄],α[Φ₁+(M−1)×360°/M,M×360°/M−Φ₁], z[z₁,z₁+th₃]);

a Y-axis magnetoresistive sensor at cylindrical coordinates(r(r=(r₁+r₂)/2), α(α=0° & 180°), z[(z=z₀−th₂)|(z=z₀+th₁+th₂)]);

an X-axis magnetoresistive sensor at cylindrical coordinates(r(r=(r₁+r₂)/2), α(α=90° & 270°), z[(z=z₀−th₂)|(z=z₀+th₁+th₂)]);

a Z-axis magnetoresistive sensor at cylindrical coordinates(r(r=(r₃+r₄)/2),α[(α=180°/M)|(α=3×180°/M)| . . . |(α=(2i−1)×180°/M)| . .. |(α=(2M−1)×360°/M)|(α=(M−1)×360°/M)],z[(z=z₁−th₄)|(z=z₁+th₃+th₄)]);

and a reference signal generator, wherein both 4N/M and M/4N arenon-integers.

In operation, the non-magnetic rotating disk rotates about a z-axis at afrequency f. An external magnetic field H is modulated by the first softferromagnetic sector into magnetic field sensed components Hx and Hyhaving a frequency of 4N×f, and the external magnetic field H is furthermodulated by the second soft ferromagnetic sector into a magnetic fieldsensed component Hz having a frequency of M×f. The three magnetic fieldsensed components Hx, Hy, and Hz are converted into output signals bymeans of the X-axis, Y-axis and Z-axis magnetoresistive sensors,respectively. The reference signal generator respectively outputs afirst reference signal having a frequency of 4N×f and a second referencesignal having a frequency of M×f. The first reference signal, the secondreference signal, and the measurement signals are demodulated by anexternal processing circuit to output magnetic field values Hx, Hy, andHz, so as to measure a three-dimensional magnetic field signal with highsignal to noise ratio.

In the embodiment of the present invention, the type of rotating diskmagnetic field probe includes a non-magnetic rotating disk, 4N firstsoft ferromagnetic sectors, M second soft ferromagnetic sectors, areference signal generator, and X-axis, Y-axis and Z-axismagnetoresistive sensors. Both the first soft ferromagnetic sectors andthe second soft ferromagnetic sectors are located on the non-magneticrotating disk, and the X-axis, Y-axis and Z-axis magnetoresistivesensors are located above or below the non-magnetic rotating disk. Inthe embodiment of the present invention, the type of rotating diskmagnetic field probe modulates a static magnetic field into ahigh-frequency magnetic field, and measures in the high-frequencymagnetic field, which can effectively overcome noise caused by a DCoffset of a TMR magnetoresistive sensor, eliminate the influence of theDC offset, and greatly reduce the noise during use of the TMRmagnetoresistive sensor. Moreover, the measurement structure is simplein manufacturing method, which can be realized by adding a rotating softferromagnetic probe to the magnetoresistive sensor, thereby reducing thecomplexity and size of the measurement structure. The measurementstructure is valuable for monitoring the geomagnetic field and improvingthe signal-to-noise ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly explain the embodiments of the presentinvention or the technical solutions in the prior art, accompanyingdrawings that need to be used in the description of the embodiments ofthe prior art will be briefly introduced below. Obviously, although theaccompanying drawings in the following description are some specificembodiments of the present invention, for those skilled in the art, theymay be expanded and extended to other structures and drawings accordingto basic concepts of the device structures, the driving method, and themanufacturing method disclosed according to the various embodiments ofthe present invention, which undoubtedly fall within the scope of claimsof the present invention.

FIG. 1 is a schematic diagram of a type of rotating disk magnetic fieldprobe according to an embodiment of the present invention;

FIG. 2 is a sectional view of FIG. 1 along B-B;

FIG. 3 is a sectional view of FIG. 1 along B-B;

FIG. 4 is a schematic diagram of rotation of FIG. 1 ;

FIG. 5 a is a diagram of a location of a maximum value of an inducedmagnetic field of a Y-axis magnetoresistive sensor;

FIG. 5 b is a diagram of a location of a minimum value of an inducedmagnetic field of a Y-axis magnetoresistive sensor;

FIG. 6 a is a diagram of a location of a maximum value of an inducedmagnetic field of an X-axis magnetoresistive sensor;

FIG. 6 b is a diagram of a location of a minimum value of an inducedmagnetic field of an X-axis magnetoresistive sensor;

FIG. 7 a is a diagram of a location of a maximum value of an inducedmagnetic field of a Z-axis magnetoresistive sensor;

FIG. 7 b is a diagram of a location of a minimum value of an inducedmagnetic field of a Z-axis magnetoresistive sensor;

FIG. 8 a is a diagram of an induced magnetic field intensity of anX-axis magnetoresistive sensor varying with a rotation angle of anon-magnetic rotating disk under an X-axis unidirectional magneticfield;

FIG. 8 b is a diagram of an induced magnetic field intensity of a Z-axismagnetoresistive sensor varying with a rotation angle of a non-magneticrotating disk under a Z-axis unidirectional magnetic field;

FIG. 9 is a white noise spectrum diagram of a magnetoresistive sensor;

FIG. 10 is a schematic structural diagram of an external processingcircuit;

FIG. 11 is a schematic structural diagram of an external processingcircuit;

FIG. 12 is a schematic diagram of a driving structure of a non-magneticrotating disk; and

FIG. 13 is a schematic structural diagram of a magnetically shieldedmotor.

DETAILED DESCRIPTION

In order to make the objectives, technical solutions, and advantages ofthe present disclosure clearer, the technical solutions of the presentdisclosure will be described clearly and completely through theimplementation manners below with reference to the accompanying drawingsin the embodiments of the present disclosure. Obviously, the describedembodiments are some embodiments but not all embodiments of the presentdisclosure. Based on basic concepts disclosed and prompted by theembodiments in the present invention, all other embodiments obtained bythose skilled in the art belong to the protection scope of the presentinvention.

Referring to FIG. 1 , a schematic diagram of a type of rotating diskmagnetic field probe according to an embodiment of the present inventionis shown. FIG. 2 is a sectional view of FIG. 1 along B-B, FIG. 3 is asectional view of FIG. 1 along B-B; and FIG. 4 is a schematic diagram ofrotation of FIG. 1 . The type of rotating disk magnetic field probe 1includes a non-magnetic rotating disk 2, 4N first soft ferromagneticsectors 3 and M second soft ferromagnetic sectors 4. Both the first softferromagnetic sectors 3 and the second soft ferromagnetic sectors 4 arelocated on the non-magnetic rotating disk 2. Cylindrical coordinates ofthe 4N first soft ferromagnetic sectors 3 are respectively (r[r₁,r₂],α[Φ₀,90°/N−Φ₀], z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+90°/N,2×90°/N−Φ₀],z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+(i−1)×90° N,i×90°/N−Φ₀], z[z₀,z₀+th₁])and (r[r₁,r₂], α[Φ₀+(4N−1)×90°/N,4N×90°/N−Φ₀], z[z₀,z₀+th₁]), andcylindrical coordinates of the M second soft ferromagnetic sector 4 arerespectively (r[r₃,r₄], α[Φ₁,360°/M−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄],α[Φ₁+360°/M,2×360°/M−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄],α[Φ₁+(i−1)×360°/M,i×360°/M−Φ₁], z[z₁,z₁+th₃]) and (r[r₃,r₄],α[Φ₁+(M−1)×360°/M,M×360°/M−Φ₁], z[z₁,z₁+th₃]); Y-axis magnetoresistivesensors 5 and 6 at cylindrical coordinates (r(r=(r₁+r₂)/2), α(α=0° &180°), z[(z=z₀−th₂)|(z=z₀+th₁+th₂)]); X-axis magnetoresistive sensor 7and 8 at cylindrical coordinates (r(r=(r₁+r₂)/2), α(α=90° & 270°),z[(z=z₀−th₂)|(z=z₀+th₁+th₂)]); a Z-axis magnetoresistive sensor 9 atcylindrical coordinates (r(r=(r₃+r₄)/2),α[(α=180°/M)|(α=3×180°/M)| . . .|(α=(2i−1)×180°/M)| . . .|(α=(2M−1)×360°/M)|(α=(M−1)×360°/M)],z[(z=z₁−th₄)|(z=z₁+th₃+th₄)]); anda reference signal generator, wherein both 4N/M and M/4N arenon-integers.

In operation, the non-magnetic rotating disk 2 rotates about a z-axis ata frequency f. An external magnetic field H is modulated by the firstsoft ferromagnetic sector 3 into magnetic field sensed components Hx andHy having a frequency of 4N×f, and the external magnetic field H isfurther modulated by the second soft ferromagnetic sector 4 into amagnetic field sensed component Hz having a frequency of M×f. The threemagnetic field sensed components Hx, Hy, and Hz are converted intooutput signals by means of the X-axis, Y-axis and Z-axismagnetoresistive sensors, respectively. The reference signal generatorrespectively outputs a first reference signal having a frequency of 4N×fand a second reference signal having a frequency of M×f. The firstreference signal, the second reference signal, and the measurementsignals are demodulated by an external processing circuit to outputmagnetic field values Hx, Hy, and Hz, so as to measure a highsignal-to-noise ratio of a three-dimensional magnetic field signal.

In this embodiment, the non-magnetic rotating disk 2 has a circularstructure with a certain thickness, and optionally may be a cylindersubstrate with a small thickness. An xyz coordinate system isestablished by taking a central axis of the non-magnetic rotating disk 2as a z=0 axis, where a plane composed of an X-axis and a Y-axis isparallel to upper and lower surfaces of the non-magnetic rotating disk2, and the Z-axis direction is perpendicular to the surface of thenon-magnetic rotating disk 2, that is, parallel to the thicknessdirection of the non-magnetic rotating disk 2. Optionally, the zcoordinate of the lower surface of the non-magnetic disk 2 is z=z₀, andthe thickness of the non-magnetic rotating disk 2 is th1, then the zcoordinate of its upper surface is z=z₀+th1. The z coordinate of thedevice below the lower surface of the non-magnetic rotating disk 2 isless than z₀, and the z coordinate of the device above the upper surfaceof the non-magnetic rotating disk 2 is greater than z₀+th1. A coordinatepoint of the device in the type of rotating disk magnetic field probe 1is represented by cylindrical coordinates (r, α, z), where r representsa vertical distance with the z-axis, and α represents an included anglebetween a projection of r on the X-Y plane and the X-axis. Optionally,the non-magnetic rotating disk 2 may be made of any non-magneticmaterial such as plastic, ceramic, metal, or polymer.

In this embodiment, the 4N first soft ferromagnetic sectors 3 arelocated on the non-magnetic rotating disk 2. Assuming N=2, thenon-magnetic rotating disk 2 as shown in FIG. 1 has 8 first softferromagnetic sectors 3, which are 3(1) to 3(8) respectively. In theoriginal state, a first soft ferromagnetic sector 3 in a first quadrantof the xy coordinate next to the +X-axis is marked as 3(1), and theremaining 7 sectors are marked as 3(2) to 3(8) counterclockwisesequentially. It is understandable that with the rotation of thenon-magnetic rotating disk 2, 3(1) will rotate to different positions.The cylindrical coordinates of the 8 first soft ferromagnetic sectors 3are respectively (r[r₁,r₂], α[Φ₀,45°−Φ₀], z[z₀,z₀+th₁]), (r[r₁,r₂],α[Φ₀+45°,90°−Φ₀], z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+90°,135°−Φ₀],z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+135°,180°−Φ₀], z[z₀,z₀+th₁]), (r[r₁,r₂],α[Φ₀+180°,225°−Φ₀],z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+225°,270°−Φ₀],z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+270°,315°−Φ₀], z[z₀,z₀+th₁]), and(r[r₁,r₂], α[Φ₀+315°,360°−Φ₀],z[z₀,z₀+th₁]). It is understandable thatin other embodiments, optionally, N=1 or N is a positive integer greaterthan or equal to 3.

The cylindrical coordinates of one first soft ferromagnetic sector 3 ofthe 4N first soft ferromagnetic sector 3 are (r[r₁,r₂], α[Φ₀,45°−Φ₀],z[z₀,z₀+th₁]), indicating that the first soft ferromagnetic sector 3 islocated in the non-magnetic rotating disk 2, the upper surface of thefirst soft ferromagnetic sector 3 is superposed with the upper surfaceof the non-magnetic rotating disk 2, the lower surface of the first softferromagnetic sector 3 is superposed with the lower surface of thenon-magnetic rotating disk 2, the thickness of the first softferromagnetic sector 3 is equal to the thickness of the non-magneticrotating disk 2, and the first soft ferromagnetic sector 3 is enclosedby two radius lines and two arcs, where an included angle between oneradius line and the x-axis is Φ₀ and an included angle between the otherradius line and the x-axis is 45°−Φ₀, one arc is located on a circlewith a radius r₂ and the other arc is located on a circle with a radiusr₁. Optionally, an included angle between the two radius lines of thefirst soft ferromagnetic sector 3 is less than 90°.

In this embodiment, the M second soft ferromagnetic sectors 4 arelocated on the non-magnetic rotating disk 2. Assuming M=5, thenon-magnetic rotating disk 2 as shown in FIG. 1 has 5 second softferromagnetic sectors 4, which are 4(1) to 4(5) respectively. In theoriginal state, a second soft ferromagnetic sector 4 in a first quadrantof the xy coordinate next to the +X-axis is marked as 4(1), and theremaining four sectors are marked as 4(2) to 4(5) counterclockwisesequentially. It is understandable that with the rotation of thenon-magnetic rotating disk 2, 4(1) will rotate to different positions.The cylindrical coordinates of the 5 second soft ferromagnetic sectors 4are respectively (r[r₃,r₄], α[Φ₁,72°−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄],α[Φ₁+72°,144°−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄], α[Φ₁+144°,216°−Φ₁],z[z₁,z₁+th₃]), (r[r₃,r₄], α[Φ₁+216°,288°−Φ₁], z[z₁,z₁+th₃]), and(r[r₃,r₄], α[Φ₁+288°,360°−Φ₁], z[z₁,z₁+th₃]). It is understandable thatN and M are integers, but 4N/M is not an integer and M/4N is not aninteger. In other embodiments, optionally, M=3, or a positive integer Mmay be reasonably selected after N is determined.

Optionally, the type of rotating disk magnetic field probe 1 furtherincludes two X-axis magnetoresistive sensors 7 and 8, two Y-axismagnetoresistive sensors 5 and 6, and a Z-axis magnetoresistive sensor9. Optionally, the Y-axis magnetoresistive sensor 5 is located at α=0°position, the Y-axis magnetoresistive sensor 6 is located at α=180°position, the X-axis magnetoresistive sensor 7 is located at α=90°position, and the X-axis magnetoresistive sensor 8 is located at α=270°position.

In this embodiment, optionally, the X-axis, Y-axis, and Z-axismagnetoresistive sensors are all located below the non-magnetic rotatingdisk 2. The cylindrical coordinates of the Y-axis magnetoresistivesensor 5 are (r(r=(r₁+r₂)/2), α(α=0°), z(z=z₀−th₂)), the cylindricalcoordinates of the Y-axis magnetoresistive sensor 6 are (r(r=(r₁+r₂)/2),α(α=180°), z(z=z₀−th₂)), the cylindrical coordinates of the X-axismagnetoresistive sensor 7 are (r(r=(r₁+r₂)/2), α(α=90°), z(z=z₀−th₂)),the cylindrical coordinates of the X-axis magnetoresistive sensor 8 are(r(r=(r₁+r₂)/2), α(α=270°), z(z=z₀−th₂)), and the cylindricalcoordinates of Z-axis magnetoresistive sensor 9 are (r(r=(r₃+r₄)/2),α(α=180°/M), z(z=z₁−th₄)).

In other embodiments, as shown in FIG. 3 , optionally, the X-axis,Y-axis, and Z-axis magnetoresistive sensors may all be located above thenon-magnetic rotating disk 2. The cylindrical coordinates of the Y-axismagnetoresistive sensor 5 are (r(r=(r₁+r₂)/2), α(α=0°),z(z=z₀+th₁+th₂)), the cylindrical coordinates of the Y-axismagnetoresistive sensor 6 are (r(r=(r₁+r₂)/2), α(α=180°),z(z=z₀+th₁+th₂)), the cylindrical coordinates of the X-axismagnetoresistive sensor 7 are (r(r=(r₁+r₂)/2), α(α=90°),z(z=z₀+th₁+th₂)), the cylindrical coordinates of the X-axismagnetoresistive sensor 8 are (r(r=(r₁+r₂)/2), α(α=270°),z(z=z₀+th₁+th₂)), and the cylindrical coordinates of the Z-axismagnetoresistive sensor 9 are (r(r=(r₃+r₄)/2), α(α=180°/M),z(z=z₁−th₄)).

In other embodiments, optionally, the cylindrical coordinates of theZ-axis magnetoresistive sensor may also be (r(r=(r₃+r₄)/2),α(α=3×180°/M), z(z=z₁−th₄)), or (r(r=(r₃+r₄)/2), α(α=5×180°/M),z(z=z₁−th₄)), or (r(r=(r₃+r₄)/2), α(α=7×180°/M), z(z=z₁−th₄)), or(r(r=(r₃+r₄)/2), α(α=9×180°/M), z(z=z₁−th₄)).

It is understandable that z₀ and z₁ are both greater than or equal to 0,th₁, th₂, th₃, and th₄ are all greater than 0, z₀ and z₁ may be equal orunequal, and any two values in th₁, th₂, th₃, and th₄ may be equal orunequal. No specific definition is made in the present invention. On thebasis of not affecting the operation of the type of rotating diskmagnetic field probe, relevant practitioners may reasonably set theplurality of values.

In this embodiment, the type of rotating disk magnetic field probe 1further includes a reference signal generator and a rotating shaft 12.Optionally, a rotating direction of the rotating shaft 12 is clockwiseas shown in an arrow direction in FIG. 4 .

In operation, the rotating shaft 12 rotates at the frequency f tosynchronously drive the non-magnetic rotating disk 2 to rotate about thez-axis at the frequency f. The three-dimensional external magnetic fieldH is modulated by the first soft ferromagnetic sector 3 into themagnetic field sensed components Hx and Hy having the frequency of 4N×f,and the three-dimensional external magnetic field H is further modulatedby the second soft ferromagnetic sector 4 into the magnetic field sensedcomponent Hz having the frequency of M×f. The magnetic field sensedcomponent Hx is measured by the X-axis magnetoresistive sensors 7 and 8respectively and X-axis measurement signals are output. The magneticfield sensed component Hy is measured by the Y-axis magnetoresistivesensors 5 and 6 respectively and Y-axis measurement signals are output.The magnetic field sensed component Hz is measured by the Z-axismagnetoresistive sensor 9 and a Z-axis measurement signal is output. Thereference signal generator outputs the first reference signal having thefrequency of 4N×f and the second reference signal having the frequencyof M×f. The first reference signal, the second reference signal, and theX-axis, Y-axis and Z-axis measurement signals are all output to theexternal processing circuit. The external processing circuit demodulatesthe received reference signals and measurement signals to obtain Hx, Hy,and Hz values and output the three magnetic field values, so as tomeasure a high signal-to-noise ratio of the magnetic field signal of thethree-dimensional external magnetic field H.

As shown in FIG. 5 a and FIG. 5 b , schematic measurement diagrams ofthe Y-axis magnetoresistive sensor are shown. FIG. 5 a shows a locationof a maximum value of an induced magnetic field. At this time, apositive projection of the Y-axis magnetoresistive sensor 5 on thenon-magnetic rotating disk 2 is located in a gap between two adjacentfirst soft ferromagnetic sectors 3(1) and 3(2). The amplitude of theinduced magnetic field in the Y-direction is the largest, and a spanradian angle of a single sector is Φ. FIG. 5 b shows a location of aminimum value of the induced magnetic field, and at this time, arotation angle of the first soft ferromagnetic sector 3(2) is θ=Φ/2. Thepositive projection of the Y-axis magnetoresistive sensor 5 on thenon-magnetic rotating disk 2 is located in the middle of the first softferromagnetic sector 3(2). The magnetic field shielding effect is thelargest, and therefore, the amplitude of the induced magnetic field inthe Y-direction is the smallest.

As shown in FIG. 6 a and FIG. 6 b , schematic measurement diagrams ofthe X-axis magnetoresistive sensor are shown. FIG. 6 a shows a locationof a maximum value of an induced magnetic field. At this time, apositive projection of the X-axis magnetoresistive sensor 7 on thenon-magnetic rotating disk 2 is located in a gap between two adjacentfirst soft ferromagnetic sectors 3(3) and 3(4). The amplitude of theinduced magnetic field in the X-direction is the largest, and a spanradian of a single sector is Φ. FIG. 6 b shows a location of a minimumvalue of the induced magnetic field, and at this time, a rotation angleof the first soft ferromagnetic sector 3(3) is θ=Φ/2. The positiveprojection of the X-axis magnetoresistive sensor 7 on the non-magneticrotating disk 2 is located in the middle of the first soft ferromagneticsector 3(3). The magnetic field shielding effect is the largest, andtherefore, the amplitude of the induced magnetic field in theX-direction is the smallest.

As shown in FIG. 7 a and FIG. 7 b , schematic measurement diagrams ofthe Z-axis magnetoresistive sensor are shown. FIG. 7 a shows a locationof a maximum value of an induced magnetic field. At this time, apositive projection of the Z-axis magnetoresistive sensor 9 on thenon-magnetic rotating disk 2 is located directly below or above one ofthe second soft ferromagnetic sectors 4(2). The amplitude of the inducedmagnetic field in the Z-direction is the largest, and a span radian of asingle sector is Φ1. FIG. 7 b shows a location of a minimum value of theinduced magnetic field, and at this time, a rotation angle of the secondmagnetic sector 4(2) is θ1=Φ1/2. The positive projection of the Z-axismagnetoresistive sensor 9 on the non-magnetic rotating disk 2 is locatedin a gap between two adjacent second soft ferromagnetic sectors 4(2) and4(3). The magnetic field shielding effect is the largest, and therefore,the amplitude of the induced magnetic field in the Z-direction is thesmallest.

As shown in FIG. 8 a , it is a diagram of an induced magnetic fieldintensity of an X-axis magnetoresistive sensor varying with a rotationangle of a non-magnetic rotating disk under an X-axis unidirectionalmagnetic field. As can be seen, in a rotation angle range of 0°-360°, anX-axis magnetoresistive sensor signal varies periodically at a period of45°. In this embodiment, it is selected that there are 8 first softferromagnetic sectors 3 in the range of 0°-360°, with a span of 45°.Therefore, assuming that a rotating frequency of the non-magneticrotating disk is f, the frequency of the X-axis magnetoresistive sensoris 8*f.

At the same time, it can be seen that variations in the induced magneticfield intensity of the Y-axis magnetoresistive sensor along with theangle of the non-magnetic rotating disk under the condition of theY-axis unidirectional magnetic field are consistent with variations inthe magnetic field intensity of the X-axis magnetoresistive sensor alongwith the rotation angle of the non-magnetic rotating disk under thecondition of the X-axis unidirectional magnetic field, and a resultthereof is similar to that in FIG. 8 a.

As shown in FIG. 8 b , it is a diagram of an induced magnetic fieldintensity of a Z-axis magnetoresistive sensor varying with a rotationangle of a non-magnetic rotating disk under a Z-axis unidirectionalmagnetic field. As can be seen, in a rotation angle range of 0°-360°, aZ-axis magnetoresistive sensor signal varies periodically at a period of72°. In this embodiment, it is selected that there are 5 second softferromagnetic sectors 4 in the range of 0°-360°, with a span of 72°.Therefore, assuming that a rotation frequency of the non-magneticrotating disk is f, the frequency of the Z-axis magnetoresistive sensoris 5*f.

As shown in FIG. 9 , it is a white noise spectrum diagram of amagnetoresistive sensor. The white noise has a 1/f feature, that is, thenoise of the magnetoresistive sensor is large at a low frequency of 140,while the noise of the magnetoresistive sensor is greatly reduced at ahigh frequency above 150. Therefore, by introducing a non-magneticrotating disk and setting 4N first soft ferromagnetic sectors and Msecond soft ferromagnetic sectors on it, the measurement magnetic fieldsHx, Hy, and Hz are modulated to frequencies 4N*f and M*f respectively,so as to reduce the white noise and improve the signal-to-noise ratio.

In the embodiment of the present invention, the type of rotating diskmagnetic field probe includes a non-magnetic rotating disk, 4N firstsoft ferromagnetic sectors, M second soft ferromagnetic sectors, areference signal generator, and X-axis, Y-axis and Z-axismagnetoresistive sensors. Both the first soft ferromagnetic sectors andthe second soft ferromagnetic sectors are located on the non-magneticrotating disk, and the X-axis, Y-axis and Z-axis magnetoresistivesensors are located above or below the non-magnetic rotating disk. Inoperation, the non-magnetic rotating disk rotates about a z-axis at afrequency f. An external magnetic field is modulated by the first softferromagnetic sector into magnetic field sensed components Hx and Hyhaving a frequency of 4N×f, and the external magnetic field is furthermodulated by the second soft ferromagnetic sector into a magnetic fieldsensed component Hz having a frequency of M×f. The three magnetic fieldsensed components Hx, Hy, and Hz are converted into output signals bymeans of the X-axis, Y-axis and Z-axis magnetoresistive sensors,respectively. The reference signal generator respectively outputs afirst reference signal having a frequency of 4N×f and a second referencesignal having a frequency of M×f. The first reference signal, the secondreference signal, and the measurement signals are demodulated by anexternal processing circuit to output magnetic field values Hx, Hy, andHz, so as to measure a high signal-to-noise ratio of a three-dimensionalmagnetic field signal. In the embodiment of the present invention, thetype of rotating disk magnetic field probe modulates the static magneticfield into a high-frequency magnetic field, and performs measurement inthe high-frequency magnetic field, which can effectively overcome thenoise caused by a DC offset of the tunnel magnetoresistance (TMR)magnetoresistive sensor, eliminate the influence of the DC offset, andgreatly reduce the noise during use of the TMR magnetoresistive sensor.Moreover, the measurement structure is simple in manufacturing method,which can be realized by adding a rotating soft ferromagnetic probe tothe magnetoresistive sensor, thereby reducing the complexity and size ofthe measurement structure. The measurement structure is valuable formonitoring the geomagnetic field and improving the signal-to-noiseratio.

For example, on the basis of the above technical solution, withreference to FIG. 1 to FIG. 4 , the non-magnetic rotating disk 2optionally has 4N first light incident holes 10 and M second lightincident holes 11. Cylindrical coordinates of the 4N first lightincident holes 10 are respectively (r(r=r_(e1)), α(α=θ&θ+90°/N&θ+2×90°/N. . . &θ+(i−1)×90°/N . . . &θ+(4N−1)×90°/N), z[z₀,z₀+th₁]), andcylindrical coordinates of the M second light incident holes 11 arerespectively (r(r=r_(e2)), α(α=θ₁&θ₁+360°/M& θ₁+2×360°/M . . .&θ₁+(i−1)×360°/M . . . &θ₁+(M−1)×360°/M), z[z₀,z₀+th₁]), where r₁<r_(e1)and r₁<r_(e2).

The reference signal generator includes a first light-emitting element161, a second light-emitting element 162, a first photodetector 14, asecond photodetector 15, a first logic trigger circuit, and a secondlogic trigger circuit. The first light-emitting element 161 is locatedabove or below the first light incident hole 10, the secondlight-emitting element 162 is located above or below the second lightincident hole 11, the first photodetector 14 is located at the otherside of the first light incident hole 10 opposite to the firstlight-emitting element 161, and the second photodetector 15 is locatedat the other side of the second light incident hole 11 opposite to thesecond light-emitting element 162.

In operation, the non-magnetic rotating disk 2 rotates about the z-axisat the frequency f. When the first light incident hole 10 and the secondlight incident hole 11 directly face the first light emitting element161 and the second light emitting element 162 in turn, the firstphotodetector 14 triggers the first logic trigger circuit to output afirst reference signal having a frequency of 4N×f, and the secondphotodetector 15 triggers the second logic trigger circuit to output asecond reference signal having a frequency of M×f. This embodiment alsouses the above accompanying drawings and reference numerals.

In this embodiment, if it is set that N=2, 8 first light incident holes10 penetrate the upper and lower surfaces of the non-magnetic rotatingdisk 2, which are respectively 10(1) to 10(8). In an original state, afirst light incident hole 10 in a first quadrant of the xy coordinateadjacent to the +X-axis or a first light incident hole 10 overlappedwith the +X-axis is marked as 10(1), and the remaining seven lightincident holes are marked counterclockwise sequentially as 10(2) to10(8). It is understandable that with the rotation of the non-magneticrotating disk 2, 10(1) will rotate to different positions. Cylindricalcoordinates of the 8 first light incident holes 10 are respectively(r(r=r_(e1)), α(α=θ), z[z₀,z₀+th₁]), (r(r=r_(e1)), α(α=θ+45°),z[z₀,z₀+th₁]), (r(r=r_(e1)), α(α=θ+90°), z[z₀,z₀+th₁]), (r(r=r_(e1)),α(α=θ+135°), z[z₀,z₀+th₁]), (r(r=r_(e1)), α(α=θ+180°), z[z₀,z₀+th₁]),(r(r=r_(e1)), α(α=θ+225°), z[z₀,z₀+th₁]), (r(r=r_(e1)), α(α=θ+270°),z[z₀,z₀+th₁]), and (r(r=r_(e1)), α(α=θ+315°), z[z₀,z₀+th₁]).

In this embodiment, if it is set that M=5, 5 second light incident holes11 penetrate the upper and lower surfaces of the non-magnetic rotatingdisk 2, which are respectively 11(1) to 11(5). In an original state, asecond light incident hole 11 in a first quadrant of the xy coordinateadjacent to the +X-axis or a second light incident hole 11 overlappedwith the +X-axis are marked as 11(1), and the remaining four lightincident holes are marked counterclockwise sequentially as 11(2) to11(5). It is understandable that with the rotation of the non-magneticrotating disk 2, 11(1) will rotate to different positions. Cylindricalcoordinates of the 5 second light incident holes 11 are respectively(r(r=r_(e2)), α(α=θ₁), z[z₀,z₀+th₁]), (r(r=r_(e2)), α(α=θ₁+72°),z[z₀,z₀+th₁]), (r(r=r_(e2)), α(α=θ₁+144°), z[z₀,z₀+th₁]), (r(r=r_(e2)),α(α=θ₁+216°), z[z₀,z₀+th₁]), and (r(r=r_(e2)), α(α=θ₁+288°),z[z₀,z₀+th₁]).

In this embodiment, the reference signal generator includes twolight-emitting elements and two photodetectors, which are respectivelythe first light-emitting element 161 and the second light-emittingelement 162, and the first photodetector 14 and the second photodetector15. The light-emitting elements and the photodetectors are respectivelylocated on both sides of the non-magnetic rotating disk 2, so that thephotodetectors may detect the light emitted by the light-emittingelements through the light incident holes. Optionally, thephotodetectors and the magnetoresistive sensors are located on the sameside of the non-magnetic rotating disk 2.

As shown in FIG. 2 , optionally, the first light-emitting element 161 islocated above the first light incident hole 10, the secondlight-emitting element 162 is located above the second light incidenthole 11, the first photodetector 14 is located below the first lightincident hole 10, and the second photodetector 15 is located below thesecond light incident hole 11. In other embodiments, as shown in FIG. 3, it is also optional that the first light-emitting element 161 islocated below the first light incident hole 10, the secondlight-emitting element 162 is located below the second light incidenthole 11, the first photodetector 14 is located above the first lightincident hole 10, and the second photodetector 15 is located above thesecond light incident hole 11. Optionally, the light-emitting elementsare LED lights or any other applicable light-emitting elements. It isunderstandable that the positions of the light-emitting elements and thephotodetectors are fixed after being determined.

In operation, the rotating shaft 12 rotates at the frequency f tosynchronously drive the non-magnetic rotating disk 2 to rotate about thez-axis at the frequency f, so that the positions of the light incidentholes on the non-magnetic rotating disk 2 rotate. When the first lightincident hole 10 and the second light incident hole 11 are rotated todirectly face the first light-emitting element 161 and the secondlight-emitting element 162 in turn, the first photodetector 14 locatedbelow the first light incident hole 10 may detect the light emitted bythe first light-emitting element 161, then the first photodetector 14triggers the first logic trigger circuit to output the first referencesignal having the frequency of 4N×f; the second photodetector 15 locatedbelow the second light incident hole 11 may detect the light emitted bythe second light-emitting element 162, then the second photodetector 15triggers the second logic trigger circuit to output the second referencesignal having the frequency of M×f.

Optionally, the first reference signal and the second reference signalare both high-level or low-level signals. Before the first photodetectordetects the light emitted by the first light-emitting element, the levelof the first logic trigger circuit remains unchanged, and after thefirst photodetector detects the light emitted by the firstlight-emitting element, the level of the first logic trigger circuit isconverted. Before the second photodetector detects the light emitted bythe second light-emitting element, the level of the second logic triggercircuit remains unchanged, and after the second photodetector detectsthe light emitted by the second light-emitting element, the level of thesecond logic trigger circuit is converted.

It is understandable that if the non-magnetic rotating disk 2 is rotatedto the first light-emitting element 161 and the first light incidenthole 10 and the first photodetector 14 are set face to face, the firstphotodetector 14 can detect the light of the first light-emittingelement 151 and trigger the first logic trigger circuit, and the firstlogic trigger circuit switches the level of the output first referencesignal. If the non-magnetic rotating disk 2 is rotated to the firstlight-emitting element 161 and the first light incident hole 10 isinterlaced with the first photodetector 14, the first photodetector 14cannot detect the light of the first light-emitting element 161, and thefirst logic trigger circuit keeps the level of the first referencesignal unchanged. The switching process of the second reference signalis identical to that of the first reference signal and will not berepeated here.

Specifically, in operation, the non-magnetic rotating disk 2 rotatesabout the z-axis at the frequency f, and the position of the lightincident hole varies. When the first light incident hole 10(1) directlyfaces the first light-emitting element 161, the first photodetector 14detects the light of the first light-emitting element 161 and convertsthe light signal into an electrical signal, so as to detect an angulardisplacement of the non-magnetic rotating disk 2, and trigger the firstlogic trigger circuit to output the first reference signal having thefrequency of 4N×f. Optionally, the level of the first reference signalmay be a high level, and the output is maintained. Sequentially, whenthe first light incident hole 10(2) directly faces the firstlight-emitting element 161, the first photodetector 14 detects the lightof the first light-emitting element 161 and converts the light signalinto an electrical signal, so as to detect an angular displacement ofthe non-magnetic rotating disk 2, and trigger the first logical contactcircuit to switch the level of the first reference signal. At this time,the first reference signal is switched from the high level to a lowlevel having the frequency of 4N×f, and the output is maintained. Byanalogy, when the first light incident hole 10 directly faces the firstlight-emitting element 161, the first photodetector 14 triggers thefirst logic trigger circuit to switch the level of the first referencesignal. When the first light incident hole 10 is interlaced with thefirst light-emitting element 161, the level of the first referencesignal output by the first logic trigger circuit remains unchanged. Ascan be seen, the first logic trigger circuit outputs the first referencesignal composed of a high level and a low level and having the frequencyof 4N×f.

Similarly, based on the second light-emitting element 162, the secondlight incident hole 11, and the second photodetector 15, the secondlogic trigger circuit outputs the second reference signal composed of ahigh level and a low level and having the frequency of M×f.

Optionally, the first photodetector 14, the second photodetector 15, theX-axis magnetoresistive sensors 7 and 8, the Y-axis magnetoresistivesensors 5 and 6, and the Z-axis magnetoresistive sensor 9 are located onthe same circuit board 13. It is understandable that the photodetectors,the magnetoresistive sensors, the logic trigger circuits, and otherstructures are all located on the same circuit board 13. The logictrigger circuit is electrically connected to the correspondingphotodetector, but the cylindrical coordinates of the logic triggercircuit are not specifically limited.

For example, on the basis of the above technical solution, optionally,the reference signal generator includes an analog angular transducer anda frequency multiplier. The analog angular transducer monitors therotation of the non-magnetic rotating disk and outputs a sine or cosineperiodic signal that varies with the angle, and then outputs the firstreference signal having the frequency of 4N×f and the second referencesignal having the frequency of M×f respectively through the frequencymultiplier. Different from the above embodiments, the reference signalgenerator in this embodiment may be arranged on the rotating shaft. Thereference signal generator includes the analog angular transducer, andthe analog angular transducer may be used for detecting the rotation ofthe rotating shaft and outputting a sine or cosine signal having afrequency of f according to the rotation angle of the rotating shaft.The reference signal generator further includes the frequencymultiplier, and the sine or cosine signal having the frequency of fpasses through the frequency multiplier to respectively generate thefirst reference signal having the frequency of 4N×f and the secondreference signal having the frequency of M×f.

For example, on the basis of the above technical solution, optionally,the X-axis magnetoresistive sensor, the Y-axis magnetoresistive sensor,and the Z-axis magnetoresistive sensor are all linear tunnelmagnetoresistive sensors.

Optionally, the external processing circuit as shown in FIG. 10 includesa first phase-locked circuit 24, a second phase-locked circuit 28, and athird phase-locked circuit 26. The measurement signals of the Y-axismagnetoresistive sensors 5 and 6 are coupled and output to the firstphase-locked circuit 24 through a first capacitor 20, the measurementsignals of the X-axis magnetoresistive sensors 7 and 8 are coupled andoutput to the second phase-locked circuit 28 through a second capacitor22, and the measurement signal of the Z-axis magnetoresistive sensor 9is coupled and output to the third phase-locked circuit 26 through athird capacitor 21. The phase-locked circuits each include a mixer and alow-pass filter. Cut-off frequencies of the low-pass filters of thefirst phase-locked circuit 24 and the second phase-locked circuit 28 areall less than 4N×f, and a cut-off frequency of the low-pass filter ofthe third phase-locked circuit 26 is less than M×f.

Optionally, the external processing circuit further includes apre-amplifier, and the pre-amplifier is arranged between the capacitorand the phase-locked circuit. As shown in FIG. 11 , a physical quantity43 to be measured, that is, the measurement signal is formed by amodulation sensor 44 into a signal having a frequency of f, including ahigh-frequency carrier signal source Vac and its corresponding sensor441. The phase-locked circuit 42 may optionally be a phase-lockedamplifier or a phase-locked loop, including a mixer 421 and a low-passfilter 422. The modulated signal output by the modulation sensor 44 isamplified by a noise amplifier 45 to obtain a signal having a signalfrequency of f. The noise amplifier 45 is a pre-amplifier. Then, thehigh-frequency carrier signal source Vac directly outputs a referencesignal having a frequency the same as that of the signal having thefrequency of f, and the frequency signal is input to the mixer 421.After mixing, a high-frequency signal and a low-frequency signal areobtained, and then the low-frequency part is removed through thelow-pass filter 422. The noise signal will not have frequency shift;therefore, the noise of the amplifier 45 is also filtered out, andfinally a high-frequency output signal 46 without the amplifier noise isobtained.

As shown in FIG. 10 , optionally, the first reference signal isrespectively connected to the first phase-locked circuit 24 and thesecond phase-locked circuit 28. The first phase-locked circuit 24outputs a Vy signal corresponding to the Y-axis magnetic field componentof the external magnetic field H, and the second phase-locked circuit 28outputs a Vx signal corresponding to the X-axis magnetic field componentof the external magnetic field H. The second reference signal isconnected to the third phase-locked circuit 26, and the thirdphase-locked circuit 26 outputs a Vz signal corresponding to the Z-axismagnetic field component of the external magnetic field H. Optionally,the phase-locked circuit is the phase-locked amplifier shown in thefigure.

As described above, the first light incident hole 10(1) is irradiated bythe first light-emitting element 161, and the first photodetector 14converts the frequency f of the rotation of the non-magnetic rotatingdisk 2 into the first reference signal having the frequency of 4N×f. Thesecond light incident hole 11(1) is irradiated by the secondlight-emitting element 162, and the second photodetector 15 converts thefrequency f of the rotation of the non-magnetic rotating disk 2 into thesecond reference signal having the frequency of M×f. The first referencesignal is transmitted to the trigger 23 and the trigger 27 respectively,then input to a reference signal input end of the phase-locked amplifier24 through the trigger 23, for obtaining the measurement signal of thecorresponding Y-axis magnetoresistive sensor subsequently, and input toa reference signal input end of the phase-locked amplifier 28 throughthe trigger 27, for obtaining the measurement signal of thecorresponding X-axis magnetoresistive sensor subsequently. The secondreference signal is transmitted to the trigger 25, and input to areference signal input terminal of the phase-locked amplifier 26 throughthe trigger 25, for obtaining the measurement signal of thecorresponding Z-axis magnetoresistive sensor subsequently.

On the other hand, the magnetic field sensed components Hx, Hy, and Hzreceived by the X-axis magnetoresistive sensor 7, the Y-axismagnetoresistive sensor 5, and the Z-axis magnetoresistive sensor 9 areconverted to electrical signals respectively having a frequency of 4N×f,4N×f, and M×f, and the electrical signals are input to the measurementsignal input terminals of the phase-locked amplifiers 24, 26, and 28after passing through the coupling capacitors, namely, the firstcapacitor 20, the second capacitor 22, and the third capacitor 21. Inthis way, the phase-locked amplifier 24 obtains the output signal Vy ofthe Y-axis magnetic field component according to the first referencesignal output by the trigger 23 and the Y-axis measurement signal of theY-axis magnetoresistive sensor 5. The phase-locked amplifier 28 obtainsthe output signal Vx of the X-axis magnetic field component according tothe first reference signal output by the trigger 27 and the X-axismeasurement signal of the X-axis magnetoresistive sensor 7. Thephase-locked amplifier 26 obtains the output signal of the Z-axismagnetic field component according to the second reference signal outputby the trigger 25 and the Z-axis measurement signal of the Z-axismagnetoresistive sensor, so as to finally obtain vector values of theexternal magnetic field.

The reference signals corresponding to the phase-locked amplifiers 24,26, and 28 are in pulse form. The optical signals received by thephotodetectors 14 and 15 are used for exciting the triggers 23, 25, and27, and then outputting a high level and a low level respectively. Eachtime the photodetector receives an LED incident light, it will triggerthe inversion of the high level and the low level. That is, the lowlevel is output at the beginning, and before the LED incident light isreceived, the low level is maintained. After the LED incident light isreceived, the low level is switched to the high level and the high levelis maintained until the next LED incident light is received, and it willchange from the high level to the low level again.

For example, on the basis of the above technical solution, as shown inFIG. 12 and FIG. 13 , optionally, the non-magnetic rotating disk 2 isdriven by a magnetically shielded motor 29 to generate rotation, thenon-magnetic rotating disk 2 is connected to the magnetically shieldedmotor 29 through the non-magnetic transmission shaft 12, the surface ofthe magnetically shielded motor 29 is covered with a metal conductivelayer 291, and one side of the magnetically shielded motor 291 close tothe non-magnetic rotating disk 2 is covered with a soft ferromagneticmetal layer 292 for magnetic shielding. Optionally, the first softferromagnetic sectors 3, the second soft ferromagnetic sectors 4, andthe soft ferromagnetic metal layer 292 are all made of softferromagnetic alloy materials.

In this embodiment, the magnetically shielded motor 29 drives thenon-magnetic rotating disk 2 to rotate through the non-magnetictransmission shaft, that is, the rotating shaft 12. The magneticallyshielded motor 29 includes a motor 293 and the rotating shaft 12connecting the motor 293 and the non-magnetic rotating disk 2, andfurther includes the metal conductive shielding layer 291 wrapped on thesurface of the motor 293, wherein one side close to the non-magneticrotating disk 2 is further attached with a soft ferromagnetic metallayer 292. The non-magnetic rotating disk 2 is made of a non-magneticmaterial, including plastic, ceramic, metal, and polymer. The first softferromagnetic sectors, the second soft ferromagnetic sectors, and thesoft ferromagnetic metal layer are all made of soft ferromagnetic alloymaterials, that is, high permeability soft ferromagnetic materialsconsisting of Co, Fe, Ni and B, Si, C, and transition metals Nb, Cu, andZr. The soft ferromagnetic metal shielding layer 292 is used forshielding the rotating magnetic field of the motor 293 to avoidaffecting the non-magnetic rotating disk 2.

It should be noted that the above are only preferred embodiments of thepresent disclosure and applied technical principles. Those skilled inthe art will understand that the present disclosure is not limited tothe specific embodiments described herein, and various obvious changes,readjustments, combinations, and substitutions can be made by thoseskilled in the art without departing from the protection scope of thepresent disclosure. Therefore, although the present disclosure has beendescribed in detail through the above embodiments, the presentdisclosure is not limited to the above embodiments, and can also includemore other equivalent embodiments without departing from the concept ofthe present disclosure. The scope of the present disclosure is definedby the scope of the appended claims.

1. A type of rotating disk magnetic field probe, comprising: anon-magnetic rotating disk, 4N first soft ferromagnetic sectors, and Msecond soft ferromagnetic sectors, wherein both the first softferromagnetic sectors and the second soft ferromagnetic sectors arelocated on the non-magnetic rotating disk, cylindrical coordinates ofthe 4N first soft ferromagnetic sectors are respectively (r[r₁,r₂],α[Φ₀,90°/N−Φ₀], z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+90°/N, 2×90°/N−Φ₀],z[z₀,z₀+th₁]), (r[r₁,r₂], α[Φ₀+(i−1)×90° N, i×90°/N−Φ₀], z[z₀,z₀+th₁])and (r[r₁,r₂], α[Φ₀+(4N−1)×90°/N, 4N×90°/N−Φ₀], z[z₀,z₀+th₁]), andcylindrical coordinates of the M second soft ferromagnetic sectors arerespectively (r[r₃,r₄], α[Φ₁,360°/M−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄],α[Φ₁+360°/M,2×360°/M−Φ₁], z[z₁,z₁+th₃]), (r[r₃,r₄],α[Φ₁+(i−1)×360°/M,i×360°/M−Φ₁], z[z₁,z₁+th₃]) and (r[r₃,r₄],α[Φ₁+(M−1)×360°/M,M×360°/M−Φ₁], z[z₁,z₁+th₃]); a Y-axis magnetoresistivesensor at cylindrical coordinates (r(r=(r₁+r₂)/2), α(α=0° & 180°),z[(z=z₀−th₂)|(z=z₀+th₁+th₂)]); an X-axis magnetoresistive sensor atcylindrical coordinates (r(r=(r₁+r₂)/2), α(α=90° & 270°),z[(z=z₀−th₂)|(z=z₀+th₁+th₂)]); a Z-axis magnetoresistive sensor atcylindrical coordinates (r(r=(r₃+r₄)/2), α[(α=180°/M)|(α=3×180°/M)| . .. |(α=(2i−1)×180°/M)| . . . |(α=(2M−1)×360°/M)|(α=(M−1)×360°/M)],z[(z=z₁−th₄)|(z=z₁+th₃+th₄)]); and a reference signal generator, whereinboth 4N/M and M/4N are non-integers; in operation, the non-magneticrotating disk rotates about a z-axis at a frequency f, an externalmagnetic field H is modulated by the first soft ferromagnetic sectorinto magnetic field sensed components Hx and Hy having a frequency of4N×f, the external magnetic field H is further modulated by the secondsoft ferromagnetic sector into a magnetic field sensed component Hzhaving a frequency of M×f, the three magnetic field sensed componentsHx, Hy, and Hz are converted into output signals by means of the X-axis,Y-axis and Z-axis magnetoresistive sensors, respectively, the referencesignal generator respectively outputs a first reference signal having afrequency of 4N×f and a second reference signal having a frequency ofM×f, and the first reference signal, the second reference signal, andthe measurement signals are demodulated by an external processingcircuit to output magnetic field values Hx, Hy, and Hz, so as to measurea high signal-to-noise ratio of a three-dimensional magnetic fieldsignal.
 2. The type of rotating disk magnetic field probe according toclaim 1, wherein the non-magnetic rotating disk has 4N first lightincident holes and M second light incident holes, cylindricalcoordinates of the 4N first light incident holes are respectively(r(r=r_(e1)), α(α=θ&θ+90°/N&θ+2×90°/N . . . &θ+(i−1)×90°/N . . .&θ+(4N−1)×90°/N), z[z₀,z₀+th₁]), and cylindrical coordinates of the Msecond light incident holes are respectively (r(r=r_(e2)),α(α=θ₁&θ₁+360°/M&θ₁+2×360°/M . . . &θ₁+(i−1)×360°/M . . .&θ₁+(M−1)×360°/M), z[z₀,z₀+th₁]), wherein r₁<r_(e1) and r₁<r_(e2); thereference signal generator comprises a first light-emitting element, asecond light-emitting element, a first photodetector, a secondphotodetector, a first logic trigger circuit, and a second logic triggercircuit, the first light-emitting element is located above or below thefirst light incident hole, the second light-emitting element is locatedabove or below the second light incident hole, the first photodetectoris located at the other side of the first light incident hole oppositeto the first light-emitting element, and the second photodetector islocated at the other side of the second light incident hole opposite tothe second light-emitting element; and in operation, the non-magneticrotating disk rotates about the z-axis at the frequency f, when thefirst light incident hole and the second light incident hole directlyface the first light-emitting element and the second light-emittingelement in turn, the first photodetector triggers the first logictrigger circuit to output the first reference signal having thefrequency of 4N×f and the second photodetector triggers the second logictrigger circuit to output the second reference signal having thefrequency of M×f.
 3. The type of rotating disk magnetic field probeaccording to claim 1, wherein the reference signal generator comprisesan analog angular transducer and a frequency multiplier; the analogangular transducer monitors the rotation of the non-magnetic rotatingdisk, outputs a sine or cosine periodic signal that varies with theangle, and then outputs the first reference signal having the frequencyof 4N×f and the second reference signal having the frequency of M×f bythe frequency multiplier.
 4. The type of rotating disk magnetic fieldprobe according to claim 2, wherein the first reference signal and thesecond reference signal are both high-level or low-level signals; beforethe first photodetector detects light emitted by the firstlight-emitting element, a level of the first logic trigger circuitremains unchanged, and after the first photodetector detects the lightemitted by the first light-emitting element, the level of the firstlogic trigger circuit is converted; and before the second photodetectordetects light emitted by the second light-emitting element, a level ofthe second logic trigger circuit remains unchanged, and after the secondphotodetector detects the light emitted by the second light-emittingelement, the level of the second logic trigger circuit is converted. 5.The type of rotating disk magnetic field probe according to claim 2,wherein the first photodetector, the second photodetector, the X-axismagnetoresistive sensor, the Y-axis magnetoresistive sensor, and theZ-axis magnetoresistive sensor are located on the same circuit board. 6.The type of rotating disk magnetic field probe according to claim 1,wherein the X-axis magnetoresistive sensor, the Y-axis magnetoresistivesensor, and the Z-axis magnetoresistive sensor are all linear tunnelmagnetoresistive sensors.
 7. The type of rotating disk magnetic fieldprobe according to claim 6, wherein the external processing circuitcomprises a first phase-locked circuit, a second phase-locked circuit,and a third phase-locked circuit; the measurement signal of the Y-axismagnetoresistive sensor is coupled and output to the first phase-lockedcircuit through a first capacitor, the measurement signal of the X-axismagnetoresistive sensor is coupled and output to the second phase-lockedcircuit through a second capacitor, and the measurement signal of theZ-axis magnetoresistive sensor is coupled and output to the thirdphase-locked circuit through a third capacitor, wherein the phase-lockedcircuits each comprise a mixer and low-pass filter, cut-off frequenciesof the low-pass filters of the first phase-locked circuit and the secondphase-locked circuit are both less than 4N×f, and a cut-off frequency ofthe low-pass filter of the third phase-locked circuit is less than M×f.8. The type of rotating disk magnetic field probe according to claim 7,wherein the external processing circuit further comprises apre-amplifier, and the pre-amplifier is arranged between the capacitorand the phase-locked circuit.
 9. The type of rotating disk magneticfield probe according to claim 7, wherein the first reference signal isrespectively connected to the first phase-locked circuit and the secondphase-locked circuit, the first phase-locked circuit outputs a Vy signalcorresponding to the Y-axis magnetic field component of the externalmagnetic field H, and the second phase-locked circuit outputs a Vxsignal corresponding to the X-axis magnetic field component of theexternal magnetic field H; and the second reference signal is connectedto the third phase-locked circuit, and the third phase-locked circuitoutputs a Vz signal corresponding to the Z-axis magnetic field componentof the external magnetic field H.
 10. The type of rotating disk magneticfield probe according to claim 1, wherein the non-magnetic rotating diskis driven to rotate by a magnetically shielded motor, the non-magneticrotating disk is connected to the magnetically shielded motor through anon-magnetic transmission shaft, the surface of the magneticallyshielded motor is covered with a metal conductive layer, and one side ofthe magnetically shielded motor close to the non-magnetic rotating diskis covered with a soft ferromagnetic metal layer for magnetic shielding.11. The type of rotating disk magnetic field probe according to claim10, wherein the first soft ferromagnetic sectors, the second softferromagnetic sectors, and the soft ferromagnetic metal layer are allmade of soft ferromagnetic alloy materials.